This application claims priority under 35 U.S.C. .sctn. 119 of European Patent Application No. 97108244.1 filed in the European Patent Office on May 21, 1997.
This invention relates to guidewires as commonly used for positioning catheters through blood vessels or for detecting blood pressure in vascular configurations.
Typically a guiding catheter may be inserted through the vasculature and the guidewire is inserted into a blood vessel via the guiding catheter. A balloon catheter may then be pushed over the guidewire for proper location into the blood vessel; alternatively, where the guidewire is for use with a pressure measuring equipment, the guidewire allows detection of the blood pressure, for example in the vicinity of a stenosis.
Usually, the distal end of the guidewire is shapeable to conform with the tortuous pathways of the blood vessels, and the shaft of the guidewire must have a good kink resistance to assure pushability of the guidewire and the transmission of torque thereto. A further requirement is that the distal end of the guidewire be radiopaque to allow tracking of the guidewire along the vasculature.
More specifically, this invention is directed to a guidewire comprising an elongated flexible shaft with a proximal portion and a distal tubular portion, a coaxial coil assembly at the distal portion of said shaft, said coaxial coil assembly comprising a first coil having a proximal portion and a distal portion, the proximal portion of said first coil being inserted into the distal tubular portion of the shaft, a second coil having a proximal portion joined to the distal portion of the first coil and a distal portion terminating into a tip, and an adhesive bond for the proximal portion of the first coil in the distal tubular portion of the shaft.
A guidewire of that kind is described in EP 0 729 765 A1. In the guidewire of that document, the proximal portion of the first coil is threadedly force fitted into the tubular distal portion of the shaft, whereby the first coil makes a thread way into the tubular distal portion of the shaft. In one embodiment, the proximal portion of the first coil has adjacent windings that are spaced apart in order to facilitate the threadingly fitting into the tubular portion of the shaft. This configuration also allows the sucking and full penetration of an adhesive into the proximal portion of the coil to secure the definite locking of the proximal portion of the coil in the distal portion of the shaft.
This guidewire results in a shape conforming assembly which has all the advantages of a threaded assembly without the need to specially machine a thread in the tubular portion of the shaft. And as the first coil makes the thread way into the tubular portion of the shaft, the assembly is largely tolerance free, of course within the limits of a given range of tolerances. However, if the assembly between the proximal portion of the first coil and the tubular portion of the shaft exceeds the limits of the tolerances admitted for the assembly, there may be problems in securing the assembly. If the outer diametral size of the proximal portion of the first coil is too largely bigger than the inner diameter of the tubular portion of the shaft, there may be difficulties to threadedly insert the proximal portion of the first coil into the tubular portion of the shaft, with the risk of breaking the coil or of damaging the shaft upon doing so. When the outer diametral size of the proximal portion of the first coil is smaller than the inner diameter of the tubular portion of the shaft, the threading engagement of the coil in the tubular shaft cannot be secured; and in that case, the adhesive which is sucked and fully penetrates into the proximal portion of the first coil cannot safely help in securing the assembly.
All documents cited herein, including the foregoing, are incorporated herein by reference in their entireties for all purposes.